Electrostatic smoking



Oct. 15, 1963 J. A. DALVE ETAL' ELECTROSTATIC SMOKING Fil ed Aug. 50, 1960 INVENTORS JOHANNES A. DALVE ROBERT B. REIF WILLIAM M. ALLEN BY 5 ,ma/m

United States Patent 015 ice 3,10%,884 Patented Oct. 15, 1963 3,106,884 ELECTROSTATIC SMOKING Johannes A. Dalve, Cincinnati, and Robert B. Reif and William M. Allen, Columbus, Uhio, assignors, by mesne assignments to Hoover Bail and Bearing Company,

Saline, Mich, a corporation of Michigan Fiied Aug. 30, 1960, Ser. No. 52,893 3 Claims. (Cl. 99-261) This invention relates to the preparation of meat products, and, more particularly, it relates to an electrostatic smoking process and apparatus.

A conventional method of smoking meats consists in hanging the meat in a Smokehouse and generating an atmosphere of smoke around the meat until such time as a sutficient quantity of smoke is deposited on the meat. This process requires a substantial number of hours and is somewhat difficult to control to the extent that a uniform product is obtainable. Electrostatic smoking devices are known in the art and are based upon the principle of charging the smoke particles opposite in charge to that of the article to be smoked, so that the smoke particles are readily deposited on the meat or meat product.

Charging the smoke is accomplished with ions produced by corona discharge, either unipolar or alternating. Corona discharge occurs when Wires or points are raised to a high electrical potential. It is visible as a bluish glow in a limited region around the emitting surface. The glow is caused by intense ionization which produces large numbers of ions of both polarities. Ions with polarity opposite to that of the emitting surface rush to the surface and are neutralized. Ions of the same polarity as the emitting surface are repelled from the emitter. Beyond the glow, the ions repelled from the emitting surface form a region of ions of a single polarity. In their travel many of the ions bombard smoke particles and the charged ions are captured by the smoke. The polarity of the corona can be changed so that the smoke can be charged positively or negatively in direct voltage fields or, alternately, positively and negatively in alternating fields.

Positive and negative corona differs in several respects. The glow discharge from a negatively charged wire occurs from discrete points distributed along the wire. Positive discharge is a continuous glow along the wire. A more important difference, however, is that negative corona can be maintained at higher potentials than positive corona before arcing takes place. Generally, negative corona would be preferred because efficiency of precipitation is dependent upon the applied voltage.

Two particle-charging mechanisms are present in corona discharge; the gas ions moving in an electrical field bombard the smoke, but other gas ions contact the smoke by ion diffusion. Ion bombardment is the more important mechanism in charging smoke particles larger than two microns in diameter. The following equation predicts the charge Q on a particle after time t in an electrostatic field of strength E,

D 1 2 1rN eKt Q [1+2 D+2 l+rrNeKt 1 where D is the dielectric constant of the particle of radius a, e is the electronic charge, N is the ion density, and K is the ion mobility of the gas. This equation is derived for spherical particles such as smoke. Although charging of the smoke is a function of time, most of the final charge is obtained in less than 0.01 second under normal charging conditions in air. Highest possible electrical fields obviously are desirable in charging particles. Inasmuch as the rate of charging is dependent on ion concentration, high ion concentrations also are desirable to obtain high charging rates. Ion concentration is dependent on the charging current which is related to the applied voltage 2 V by the equation, i=CV (V- V where V is the voltage at which corona admission first starts and C is a constant particular to the charging condition.

Ions in the air also obey the laws of kinetic theory. Collision will take place between ions and smoke in the gas. The charging mechanism is independent of the externally applied electrical field. The ion diffusion process is the predominant method of charging of particles less than two microns in diameter.

For the electrostatic smoking of meat products, a strand of wire is placed near the meat product which serves as a ground electrode. When the wire diameter is small and the meat product diameter is large and distance d between the wire and the product surface is large compared to the wire diameter, the electrical fields intensity E is given approximately by the equation:

where V is the applied voltage, -R is the radius of the wire, and r is the distance from the center of the wire to any point in the field. To obtain high-intensity fields at the surface of the wire, wire of small diameter is used in the charging end and high voltages are applied on the wire.

Charged smoke is driven back onto the meat product by the forces exerted on the particles by the high-voltage electrical fields. The motion of the smoke particle toward the meat product is governed by the viscosity of the air stream, which retards the particles, and the electrical force which accelerates the particles.

In the conventional electrostatic smoking apparatus, no provision is made for preventing arcing from occurring from the electrodes to the machine parts or meat products. [his invention discloses a process and apparatus for preventing arcing so that the electrodes are not burned 011? and the high voltage source is not overloaded.

Ordinarily arcs occur in the air when the electrical field strength exceeds 30 kilovolts per centimeter. However, the equation relating field strength to applied voltage in the core of the wire and plane surface shows that electrical gradients exceeding breakdown strength of air can be obtained at the surface of a small wire with ten kilovolts, while the field strength at a few diameters from the wire does not exceed the breakdown strength. Thus, the wire emits corona, but the electrical breakdown does not extend far into the gap between the wire and the meat product. The critical field gradient at which corona will actually start has been determined to depend on the wire radius r and the smoothness of the wire which is described by a factor M. The critical field gradient necessary at the surface of the wire for corona to start is given by the equation:

From this equation and the equation relating E with V, V the applied voltage, at which corona will start, can be calculated.

The electrostatic smoking of machine-produced meat products becomes difficult where metallic parts are brought into close proximity with the Wires that carry the high electrical charge. In the specific example of this invention, sausage casings which are stuffed with a comminuted meat mixture are fed onto a conveyor which has a plurality of metallic crimping bars mounted parallel to each other between two conveyor or roller chains. The crimping bars are spaced from one another at a distance equal to the desired length of a sausage. The stuffed casings are of an extended length and are formed by the crimping bars into a number of individual discrete sausage As the stuffed casings are placed in the conveyor, the crimping bars have a large opening to receive the casings and are activated to crimp the casing automatically, and have an effect similar to a tying machine. The conveyor serves as a means of carrying the sausages through a machine which may perform a number of operations such as cooking, washing, cooling, and the smoking process of this invention. Since the crimping bars or similar carriers of other meat products may pass closer to the charged wires than the meat product itself, arcing from the wires to the conveyor may occur in conventional electrostatic smoking processes and devices where no provision is made to prevent the condition.

In accordance with this invention, there is provided a process for treating meats which comprises passing one side of the conveyor-carried meat product beneath a number of ionizing electrodes, passing smoke over the electrodes, reducing the voltage in each electrode as it is approached by the metallic parts of the conveyor and then reversing the position of the meat product to expose the opposite side of the meat product in the same manner.

Further, in accordance with this invention, there is provided electrostatic smoking apparatus comprising, a conveyor for supporting and moving meat products, a compartment for containing smoke, having a plurality of openings therein, a plurality of ionizing electrodes arranged in spaced parallel relationship between the meat and the box, each of the electrodes having means to reduce the voltage in the electrode when metallic parts of the conveyor approach the proximity of the wire, and smoke-generating apparatus for supplying smoke to the smoke box.

In accordance with still another feature of this invention, groups of electrodes are arranged in insulated units with the individual electrodes having a receptacle for plugging the electrode into the high-voltage supply. The units are removable from beneath the smoke box so that the electrodes are easily cleaned to remove smoke deposits.

One advantage of this invention is that in an electrostatic smoking apparatus in which parts of a conveyor may be nearer to the electrodes than the meat product, arcing from the electrodes to the conveyor is eliminated and prevents damage to the electrodes and high-voltage supply system. Another advantage of the apparatus of this invention is that the meat product is placed below the electrodes so that loose particles of the meat product will not fall into the smoking apparatus causing shorting and serious damage to the apparatus. Still another advantage of this invention is that provision is made for quick replacement and cleaning of the electrodes.

Other advantages and features of the invention will be understood from the accompanying drawings and the following description and claims.

In the drawings:

FIG. 1 is a perspective view of one end of the electrostatic smoking device with supporting structure omitted for clarity;

FIG. 2 is a perspective view, with a portion broken away, of one embodiment of an electrode unit in accordance with this invention;

FIG. 3 is an elevational view of a receptacle for the electrode plugs; and

FIG. 4 is a diagrammatic view of the electrodes and their relationship to the meat product conveyor.

Referring to FIG. 1 a conveyor 19 for carrying meat products is positioned below the elongated compartments or smoke boxes 11 and 12 closed at the top, at the ends, and at the sides. Although the conveyor may take a variety of forms, such as a belt or plurality of receptacles for holding individual meat products, the conveyor shown in FIG. 1 has a pair of roller chm'ns 13-13 with a plurality of crimper bars 14-14 suspended between the roller chains 13-13. The conveyor is particularly adapted for supporting, crimping, and moving elongated sausage casings. The crimping bars 14-14 are in the closed position and the casing is crimped into individual discrete sausage links 15--15. The crimping bars 14-14 are parallel and spaced apart according to the depth of sausage link 15 desired. The conveyor 10 may travel in either direction so that half of the sausages 1515 are smoked as they pass under the first smoke box 11, and the opposite sides are smoked as the conveyor 10 passes over the sprocket wheels 26-20 and travels in the opposite direction beneath the second smoke box 12. Although the smoking could be carried out in one stage by placing smoke boxes both above and below the conveyor 10, the form shown herein is preferred, since it is possible that fragments of the meat product or unattached trailing ends of the casing may, by the force of gravity, fall or hang into the apparatus if it is placed below the conveyor 16. The sprockets -2{) supporting the conveyor are rotatably mounted on a frame by suitable means, not shown.

Smoke which may be generated from a suitable material, such as hickory sawdust or shavings, is produced by suitable means, such as a smoke generator 21, and supplied by means of ducts 22 to the smoke boxes. The bottom of the smoke boxes 11 md 12 are provided with a plurality of ope ings 25--25 (shown in FIG. 2), such as slots, perpendicular to the direction of the movement of the conveyor. The openings, of course, need not be slots and may have a variety of shapes such as circles, ellipses, etc.; however, slots are a convenient shape in many respects. A number of racks 30, an example of which is shown in FIG. 2, and which are made from insulating material such as Lucite are slidably mounted on suitable mounts 31 beneath the smoke boxes.

Referring to FIG. 2, the frame or rack '30 of insulating material supports a plurality of electrodes or wires 32 arranged beneath the slots 25 and perpendicular to the direction of travel of the conveyor 10. At one end of the electrode 32 is a male plug or split-pin contact 33 which is plugged into a female receptacle or banana jack 34 (shown in FIG. 3) supported by a strip of insulating material 35 along the edge of the smoke box 12. The banana jack 34 having an opening 40, a receptacle 41 and a lead wire 42, is connected to the electrical circuit shown in FIG. 4 consisting of the high voltage supply 45 and a supply line 46. A resistor 47 is placed between the supply line 46 and the banana jack 34 (the banana jack 34 is not shown in the diagram of FIG. 4).

As shown in FIG. 4, the resistors 4747 in the circuit to the charging wires play an important part in permitting the metallic parts 50 of the conveyor 10 to pass close to the electrodes 32. Also, where the meat product has an irregular shape, some portions of the meat product may pass very close to the electrodes 32. The resistor 47 in each wire circuit or electrode circuit serves as a device which automatically reduces the voltage applied to the electrode 32 as the conveyor part 50, or an irregularly shaped meat product, approaches and passes the electrode 32. The need for the resistor 47, arises because the distance from the electrode 32 to the conveyor part 50 is less than the distance from the electrode to the meat product 15. In order for the wires 32 to emit corona while they are over the meat product 15, a potential must be applied to the electrodes 32 with the conveyor 10 and meat products connected to ground 51. If the same voltage is applied to the electrodes 32-32 over the conveyor parts 5%, or portions of the meat product which are exceptionally close to the electrodes 32, the field gradient is so high that instead of corona emission, the emission from the wires 3232 occurs as arcs which can burn off the electrodes 32 or damage electrical high voltage supply 45.

For the electrode 32 that is over the meat product 15, the normal corona current (i) will cause a voltage drop (V of Ri in the resistor 47. The voltage (V) delivered by the power supply 45 is decreased by V,., such that the voltage (V across the gap is V =V-V The size of the resistor 47 and output of the power supply 45 are selected so that the current causes a drop in the resistors 47-47 that will still deliver sufiicient voltage (V at the electrodes 32 to produce maximum useful corona. For maximum efficiency, V should be near the breakdown potential across the gap.

As the conveyor portion or crimper 5t} approaches an electrode 32, the field gradient increases and the current will increase rapidly. However, as the current (ic) increases, the voltage (V drop across the resistors 47-47 increases to R and the efiective voltage (V VV across the gap between the wire 32 and the crimper 50 decreases. In short, as the crimper 5t approaches the electrode 32, the voltage gradient starts to increase and the current increases. However, as the current increases, the resistive drop increases, the voltage across the gap decreases, and the current flow is limited. In this way, the electrode 32 can be brought near the crimper 50 without setting up field gradients that would cause arcs, thus burning off the electrode 32.

In the preferred form of the invention the racks 30 containing the wires 32-32 are arranged in a number of sections on each smoke box 12 and each section is removable for cleaning purposes. The carbon from the smoke has a tendency to deposit on the Wires 32 and reduce their electrostatic efiiciency. The racks 34) are removed and cleaned in a detergent-type material such as Oakite.

What is claimed is:

1. An electrostatic smoking apparatus for smoking food products comprising: at least one compartment for receiving and accumulating smoke having a plurality of elongated slots in the bottom thereof; a smoke generator communicating with said at least one compartment; a plurality of ionizing wire electrodes horizontally mounted positioned parallel to and below said elongated slots in the bottom of said at least one compartment; a high-voltage 7 generator connected to said electrodes; a conveyor positioned to pass beneath said at least one compartment and bring said food products in proximate relationship with said electrodes; and resistors electrically connected between said high-voltage source and said electrodes to reduce the voltage in said electrodes as said conveyor and said food products approach arcing distance to said electrodes.

2. An electrostatic smoking apparatus for smoking food products comprising: at least one compartment for receiving and accumulating smoke having a plurality of elongated slots in the bottom thereof; a smoke generator communicating with said at least one compartment; a plurality of ionizing electrodes horizontally mounted in an insulated frame parallel to and below said elongated slots in the bottom of said at least one compartment, said frame slidably mounted on the bottom of said compartment and removable therefrom; a high-voltage generator connected to said electrodes; a conveyor supporting and moving said food products positioned to pass beneath said compartments and bring said food products in proximate relationship with said electrodes; and resistors electrically connected between said high-voltage source and said electrodes to reduce the voltage of said electrodes as said conveyor comes within arcing distance of said electrodes.

3. An electrostatic smoking apparatus for smoking food products comprising: a first compartment and a second compartment enclosed to receive and accumulate smoke having a plurality of elongated slots in the bottom thereof; a smoke generator communicating with said first and second compartments; a plurality of ionizing, wire electrodes horizontally mounted in insulated frames, said electrodes parallel to and below said elongated slots in the bottom of said first and second compartments and each of said electrodes terminating in plug, each plug receivable by a receptacle supported by said compartments, said insulated frames slidably mounted on the bottom of said compartments and removable therefrom; a high-voltage generator connected to said receptacles; a conveyor supporting and moving said food products positimed to first bring one side of said food products in proximate relationship with said electrodes mounted on said first compantment and to subsequently bring the opposite side of said food products in proximate relationship with electrodes mounted on said second compartment, said conveyor being electrically grounded to make ground connection for said food products and said conveyor; and resistors electrically connected between said high voltage generator and said electrodes to reduce the voltage of said electrodes as said grounded food products and conveyor approach arcing distance to said electrodes.

Ransburgh et al. May 30, 1950 Lawrence Feb. 12, 1952 

1. AN ELECTROSTATIC SMOKING APPARATUS FOR SMOKING FOOD PRODUCTS COMPRISING: AT LEAST ONE COMPARTMENT FOR RECEIVING AND ACCUMULATING SMOKE HAVING A PLURALITY OF ELONGATED SLOTS IN THE BOTTOM THEREOF; A SMOKE GENERATOR COMMUNICATING WITH SAID AT LEAST ONE COMPARTMENT; A PLURALITY OF IONIZING WIRE ELECTRODES HORIZONTALLY MOUNTED POSITIONED PARALLEL TO AND BELOW SAID ELONGATED SLOTS IN THE BOTTOM OF SAID AT LEAST ONE COMPARTMENT; A HIGH-VOLTAGE GENERATOR CONNECTED TO SAID ELECTRODES; A CONVEYOR POSITIONED TO PASS BENEATH SAID AT LEAST ONE COMPARTMENT AND BRING SAID FOOD PRODUCTS IN PROXIMATE RELATIONSHIP WITH SAID ELECTRODES; AND RESISTORS ELECTRICALLY CONNECTED BETWEEN SAID HIGH-VOLTAGE SOURCE AND SAID ELECTRODES TO REDUCE THE VOLTAGE IN SAID ELECTRODES AS SAID CONVEYOR AND SAID FOOD PRODUCERS APPROACH ARCING DISTANCE TO SAID ELECTRODES. 